$-uv + 7v - 3w - 9 = -2v + 3w - 3$ Solve for $u$.
Combine constant terms on the right. $-uv + 7v - 3w - {9} = -2v + 3w - {3}$ $-uv + 7v - 3w = -2v + 3w + {6}$ Combine $w$ terms on the right. $-uv + 7v - {3w} = -2v + {3w} + 6$ $-uv + 7v = -2v + {6w} + 6$ Combine $v$ terms on the right. $-uv + {7v} = -{2v} + 6w + 6$ $-uv = -{9v} + 6w + 6$ Isolate $u$ $-u{v} = -9v + 6w + 6$ $u = \dfrac{ -9v + 6w + 6 }{ -{v} }$ Swap the signs so the denominator isn't negative. $u = \dfrac{ {9}v - {6}w - {6} }{ {v} }$